Enamel-coated article



Patented Nov. .27,

UNITED srATEs JOHN A. ANDERSON, OI GARDNER, MASSACHUSETTS, ASSIGNOE TO CENTRAL OID b PATENT opp-I GAS STOVE COMPANY, OF GARDNER, MASSACHUSETTS, A CORPORATION Ol' MASSA- cnusn'rrs.

no Drawing My invention relates to a new and useful vitreous enamel which is especially adapted to the protection of iron and steel from oxidation or corrosion at high temperatures by air, steam, flame gases, acids or acid fumes and the like.

A particular application of my enamel may now be described, without, however, 11miting myself solely to such use, since there are many other valuable industrial applications-that can be made of such enamel. I haye found this enamel coating very effective 1n preventing the oxidation, scaling or other detcrioration of the underlying metal frequently caused by flames at high temperature. The coating is particularly effective for protecting from such destructive eflects the inner steel or iron or other metal chimneys or cylinders used for heating oil to a vaporizing or gasifyin g temperature in oil burning stoves. These chimneys are maintained hot by thecombustion of the gas formed by vaporizing the oil, said vapors being mixed by suitable devices with the proper amount of air for perfect combustion. Such chimneys, while the stove is in operation, operate at temperatures usuallv within 1000 F. to 1600 F. I have found that without such enamel coating the useful life of steel or iron chimneys used in such stoves is quite limited, whereas properly enameled ones last almost indefinitely. I have found the enamel herein described to be eifective at temperatures higher than such stoves attain, for instance at 2000 F. to

"I will now describe the method used in manufacturing and applying one example of my enamel :A raw batch is weighed out as follows:Borax, 29%. feldspar, 23.10%, sand, 35.10%, carbonate of soda, 3.10%. fluor spar, 4.96%, nitrate of soda, 3.10%, boric acid 0.92%, nickel oxide, 0.18% and cobalt *oxide 0.73%. These materials are mixed in coarsely powdered condition and then smelted in a furnace maintained at 2400 F. to 2800 F. for about 5 hours. The molten mixture is then run into water to render it brittle by the rapid cooling. After this the material is ground in pebble mills 10 01-15 hours, there v ENAMEL-COATED ARTICLE.

Application filed December 5, 1928. Serial No. 878,784 7 plied of sufficient thickness, it is dried quickly-say within 15 minutes-and then fired for 5 to 12 minutes in a furnace maintained at 1700 to 1900 Upon removal from this furnace the pieces are cooled in the air, which completes the manufacturing operation.

I have found the following enamel composition particularly efi'ective for themetal chimney protection above described; this analysis refers to the composition obtained from the raw batch and mill additions above described-in other words to the finished enamel Per cent. Silicon oxide (SiO 6 Boron oxide (B O 13.06 Sodium oxide (Na O) 12.23 Aluminum oxide (A1 0 6. 47 Calcium oxide (CaO) 5.81 Cobalt oxide (C00) 0. 86 Nickel oxide (NiO) 0.43

In describing this composition it is to, be understood that the proportions given may be varied slightly without materially changing the results or affecting my invention.

I find that the incorporation of these high contents of silica and boric oxide in vitreous enamels for iron and steel, together with the proportions of cobaltic and nickelic oxides described, results in valuable properties new to the art. Thus, very refractory enamels are formed, which resist high temperatures and the eroding and corroding action of flame gases, and there is nocracking or development of blisters'or pores in the enamel at high or low temperatures, as is the case when ordinary vitreous enamels different in composition, are subjected to the high temperatures herein described.

The efficient protective action'of my enamel portions which I have found to give an enamel of superior properties, I have found, by many tests and experiments, that there may be certain variations in the amounts and materials of the raw batch and mill additions. lVhile in general, I find that suclrvariations donot give as good results as the enamel above described, nevertheless, there is a distinct improvement over ordinary vitreous enamels for iron or steel which do not protect the metal at high temperatures. Thus, I have made and found fairly satisfactory for flame resistance, enamels for steel and iron in which the proportions of the constituents in the raw batch have varied as follows 2-- Per cent.

Borax 28.15 to 34.72 Feldspar 21.30 to 27.69 Sand 16.90 to 35.10 Sodium carbonate 2.87 to 5.70 Fluorspar 4.56 to 5.93 Sodium nitrate- 1.69 to 3.73 Boric acid 0.90 to 1.09 Nickel oxide 0.17 to 0.35 Cobalt oxide 0.70 to 2.02

I have also foundiron oxide a desirable con stituent in addition to or substituted for nickel or cobalt oxide.

In some cases I have found an iron oxide addition of as much as 16.90% to the raw batch advantageous. In other cases I have added aluminum powder up to 9.10%.

In the mill additions I have also made variations in my experiments as follows z- Per cent. Clay 2.57 to 3.20 Boric acid 0.32 to 0.47 Iron oxide 0.0 to 11.90 Cobalt oxide 0.0 to 1.65 Nickel oxide 0.0 to 0.16

' enamel, I mean a vitreous composition prepared according to enameling technique as commonly understood 1n this art. One example of enameling technique is disclosed in this specification.

Having thus described my invention, what I- claim and desire to secure by Letters Pat- 1. As a new article of manufacture, a heat resistant object comprising a base coated with enamel whose components include 60% silica and an anchoring material.

2. As a new article of manufacture, a heat resistant object comprising a metallic base coated with an enamel Whose components include 60% silica and an anchoring material, the ratio of acid oxides to basic oxides exceeding the ratio of 3: 1.

3. As a new article of manufacture, a high heat resistant object comprising a metallic base coated with an enamel whose components include at least 40% silica, and also cobalt, nickel and iron oxides the ratio of acid oxides to basic oxides in said enamel exceeding the ratio of 3:1.

4. As a new article of manufacture, a high heat resistant object comprising a metallic base coated with an enamel whose components include at least 40% silica, and also including at least .4% nickel oxide and .8% cobalt oxide the ratio of acid oxides to basic oxides in said enamel exceeding the ratio of 5. As a new article of manufacture, a high heat resistant object comprising a metallic base coated with an enamel whose components include at least 40% silica, and the following ingredients in substantially the following percentages Boron oxide 13.06 Sodium oxide 12.23 Aluminum oxide 6.47 Calcium oxide 5.81 Cobalt oxide 0.86 Nickel oxide 0.43

6. As a new article of manufacture, a high heat resistant object comprising a metallic base coated With an enamel whose components include the following ingredients in substantially the percentages specified- Silica 60.96

Boron oxide 13.06 Sodium oxide 12.23 Aluminum oxide 6.47 Calcium oxide 5.81 Cobalt oxide 0.86 Nickel oxide 0.43

oxide 12.23%, aluminum oxide 6.47%, cal cium oxide 5.81%, cobalt oxide 0.86%, and nickel oxide 0.43%. l

10. As a new article of manufacture a heat resistant object comprising a metallic base coated with an enamel containing at least 40% silica and an anchoring material, the ratio of acid oxides to basic oxides in said enamel exceeding the ratioof 3:1.

11. As a new article of manufacture, a heat resistant object comprising a metallic base coated with an enamel containing at least 40% silica, 4% boric oxide, and an anchoring material.

12. As a new article of manufacture, a heat resistant object comprising a metallic base coated with an enamel containing at least 40% silica, 4% boric oxide, and an anchoring material, the ratio of acid oxides to basic oxides in said enamel exceeding the ratio of 3: 1.

13. As a new article of manufacture, a heat resistant object comprising a metallic base coated with an adherent enamel, to wit, a vitreous 'inaterial prepared by smelting a raw batch, coolingand pulverizing the smelted material in a mill, with mill additions, applyin the milled material to a metallic base, and tien firing the coated base, said enamel containing at least 40% silica, and an anchoring material, the ratioof acid oxides to basic oxides exceeding the ratio of 3 :1.

In testimony whereof, I aflix my signature.

JOHN A. ANDERSON. 

